The nanny for the couple's two-and-a-half-year-old son, Rennie, died suddenly in August
"It's been tough for her," Foster, 73, told Entertainment Tonight on Thursday, while McPhee agreed, briefly adding “yeah” as her husband spoke.
Foster continued, “Yeah, it’s been tough. She’s managing.”
On Aug. 11, McPhee announced on Instagram that she had to rush home, missing the last two shows of the David Foster & Friends Asia Tour 2023 as she shared, “David and I have had a horrible tragedy in our family.”
The Smash! alum didn’t give specific details as to what had occurred, but promised her fans in Jakarta, Indonesia that she would love to “return one day and perform” for them.
Several days later, sources told PEOPLE that the nanny for the couple’s two-year-old son had died suddenly. TMZ was the first to report the news.
McPhee and Foster, who wed in 2019, returned to the stage together in Italy two weeks later, which was captured in a series of videos shared on Instagram by Jersey Boys’ Erich Bergen. In the clips, McPhee sang with Bergen, 37, while her husband played the piano.
“Singing Frankie Valli and The Four Seasons songs in Italy just seems appropriate,” Bergen wrote alongside the videos of the performance, which, based on the post’s tag, took place at Villa Rufolo in Ravello, Italy. “So great to perform with my friends @davidfoster @katharinefoster.”
The performance appeared to mark Foster and McPhee’s first time back on stage together following the announcement of their family’s tragedy earlier in the month, and though none of the videos Bergen posted had sound, the singer also shared a video from the performance on his Instagram Story.
In the clip, he and McPhee were heard duetting Frankie Valli’s “Can’t Take My Eyes Off You.”
Aside from Rennie, Foster is also father to five daughters: Allison, 53; Amy, 50, whom he shares with his first wife, B.J. Cook; and Sara, Erin, 41, and Jordan, 37, all of whom he shares with second wife Rebecca Dyer.
Given the age gap between his kids — there’s 50 years between his eldest, Allison, and his son, Rennie — having such a young child has been an adjustment for the Grammy award winner.
"At this point in my life, it's different again," he told PEOPLE in January. "Not better or worse, just different. I still work, I'm still gone a lot, but maybe the time is a little more precious to me because I got more runway behind me than I have ahead of me now."
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Elsewhere in this week's ET interview, Foster and McPhee discussed their upcoming album Christmas Songs, which will be released on Oct. 20. "Amazing Grace" is slated to be the first release from the new album, and will be out Oct. 6.
"We got a nice response from the first seven songs so we thought, 'Oh, people are kinda digging this," Foster told the outlet, explaining that the new record is a "completion" of their 2022 Christmas Songs album.
"Volume two, we'll just complete the whole thing," McPhee said. "A couple of my girlfriends are like, 'You're doing another Christmas album?' I'm like, 'No, this is a completion of the first Christmas album.'"
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